Add support for attribute change callbacks in AXNodeData.

ui/accessibility/ax_tree.cc

Index: ui/accessibility/ax_tree.cc
diff --git a/ui/accessibility/ax_tree.cc b/ui/accessibility/ax_tree.cc
index 2d2a535f7e985a8ec5c0814b2628a2a05818cd77..c726a4d02f5e4b0b75035a92bd4e647b6f8bd4f3 100644
--- a/ui/accessibility/ax_tree.cc
+++ b/ui/accessibility/ax_tree.cc
@@ -24,6 +24,63 @@ std::string TreeToStringHelper(AXNode* node, int indent) {
   return result;
 }
 
+template <typename K, typename V>
+bool KeyValuePairsKeysMatch(std::vector<std::pair<K, V>> pairs1,
+                            std::vector<std::pair<K, V>> pairs2) {
+  if (pairs1.size() != pairs2.size())
+    return false;
+  for (size_t i = 0; i < pairs1.size(); ++i) {
+    if (pairs1[i].first != pairs2[i].first)
+      return false;
+  }
+  return true;
+}
+
+template <typename K, typename V>
+std::map<K, V> MapFromKeyValuePairs(std::vector<std::pair<K, V>> pairs) {
+  std::map<K, V> result;
+  for (size_t i = 0; i < pairs.size(); ++i)
+    result[pairs[i].first] = pairs[i].second;
+  return result;
+}
+
+// Given two vectors of <K, V> key, value pairs representing an "old" vs "new"
+// state, or "before" vs "after", calls a callback function for each key that
+// changed value.
+template <typename K, typename V, typename F>
+void CallIfAttributeValuesChanged(const std::vector<std::pair<K, V>>& pairs1,
+                                  const std::vector<std::pair<K, V>>& pairs2,
+                                  const V& empty_value,
+                                  F callback) {
+  // Fast path - if they both have the same keys in the same order.
+  if (KeyValuePairsKeysMatch(pairs1, pairs2)) {
+    for (size_t i = 0; i < pairs1.size(); ++i) {
+      if (pairs1[i].second != pairs2[i].second)
+        callback(pairs1[i].first, pairs1[i].second, pairs2[i].second);
+    }
+    return;
+  }
+
+  // Slower path - they don't have the same keys in the same order, so
+  // check all keys against each other, using maps to prevent this from
+  // becoming O(n^2) as the size grows.
+  auto map1 = MapFromKeyValuePairs(pairs1);
+  auto map2 = MapFromKeyValuePairs(pairs2);
+  for (size_t i = 0; i < pairs1.size(); ++i) {
+    const auto& new_iter = map2.find(pairs1[i].first);
+    if (pairs1[i].second != empty_value && new_iter == map2.end())
+      callback(pairs1[i].first, pairs1[i].second, empty_value);
+  }
+
+  for (size_t i = 0; i < pairs2.size(); ++i) {
+    const auto& iter = map1.find(pairs2[i].first);
+    if (iter == map1.end())
+      callback(pairs2[i].first, empty_value, pairs2[i].second);
+    else if (iter->second != pairs2[i].second)
+      callback(pairs2[i].first, iter->second, pairs2[i].second);
+  }
+}
+
 }  // namespace
 
 // Intermediate state to keep track of during a tree update.
@@ -228,9 +285,8 @@ bool AXTree::UpdateNode(const AXNodeData& src,
   AXNode* node = GetFromId(src.id);
   if (node) {
     update_state->pending_nodes.erase(node);
-    if (delegate_ &&
-        update_state->new_nodes.find(node) == update_state->new_nodes.end())
-      delegate_->OnNodeDataWillChange(this, node->data(), src);
+    if (update_state->new_nodes.find(node) == update_state->new_nodes.end())
+      CallNodeChangeCallbacks(node, src);
     node->SetData(src);
   } else {
     if (!is_new_root) {
@@ -291,6 +347,70 @@ bool AXTree::UpdateNode(const AXNodeData& src,
   return success;
 }
 
+void AXTree::CallNodeChangeCallbacks(AXNode* node, const AXNodeData& new_data) {
+  if (!delegate_)
+    return;
+
+  const AXNodeData& old_data = node->data();
+  delegate_->OnNodeDataWillChange(this, old_data, new_data);
+
+  if (old_data.role != new_data.role)
+    delegate_->OnRoleChanged(this, node, old_data.role, new_data.role);
+
+  if (old_data.state != new_data.state) {
+    for (int i = AX_STATE_NONE + 1; i <= AX_STATE_LAST; ++i) {
+      AXState state = static_cast<AXState>(i);
+      if (old_data.HasStateFlag(state) != new_data.HasStateFlag(state)) {
+        delegate_->OnStateChanged(this, node, state,
+                                  new_data.HasStateFlag(state));
+      }
+    }
+  }
+
+  auto string_callback = [this, node](AXStringAttribute attr,
+                                      const std::string& old_string,
+                                      const std::string& new_string) {
+    delegate_->OnStringAttributeChanged(this, node, attr, old_string,
+                                        new_string);
+  };
+  CallIfAttributeValuesChanged(old_data.string_attributes,
+                               new_data.string_attributes, std::string(),
+                               string_callback);
+
+  auto bool_callback = [this, node](AXBoolAttribute attr, const bool& old_bool,
+                                    const bool& new_bool) {
+    delegate_->OnBoolAttributeChanged(this, node, attr, new_bool);
+  };
+  CallIfAttributeValuesChanged(old_data.bool_attributes,
+                               new_data.bool_attributes, false, bool_callback);
+
+  auto float_callback = [this, node](AXFloatAttribute attr,
+                                     const float& old_float,
+                                     const float& new_float) {
+    delegate_->OnFloatAttributeChanged(this, node, attr, old_float, new_float);
+  };
+  CallIfAttributeValuesChanged(old_data.float_attributes,
+                               new_data.float_attributes, 0.0f, float_callback);
+
+  auto int_callback = [this, node](AXIntAttribute attr, const int& old_int,
+                                   const int& new_int) {
+    delegate_->OnIntAttributeChanged(this, node, attr, old_int, new_int);
+  };
+  CallIfAttributeValuesChanged(old_data.int_attributes, new_data.int_attributes,
+                               0, int_callback);
+
+  auto intlist_callback = [this, node](
+                              AXIntListAttribute attr,
+                              const std::vector<int32_t>& old_intlist,
+                              const std::vector<int32_t>& new_intlist) {
+    delegate_->OnIntListAttributeChanged(this, node, attr, old_intlist,
+                                         new_intlist);
+  };
+  CallIfAttributeValuesChanged(old_data.intlist_attributes,
+                               new_data.intlist_attributes,
+                               std::vector<int32_t>(), intlist_callback);
+}
+
 void AXTree::DestroySubtree(AXNode* node,
                             AXTreeUpdateState* update_state) {
   DCHECK(update_state);